ptuomov wrote: ↑Wed Sep 21, 2022 9:39 pm
In the case of the M139 engine that was released in 2014, I believe that the most binding constraint to making even more torque at higher rpms was cycle to cycle combustion variability, particularly pre-ignition/super knock that was traced back to oil droplets being drawn into the charge. I recall reading this from somewhere back in the day.
Juup, I've mentioned similar earlier in my posts to this that a too high squish velocity can lead to low pressure squish ring, which can suck oil from the fireland and liner wall. The M133, released in 2013 (M139 was released in 2019) does operate on peak cylinder pressures of up to 160 bar, which is quite similar to that what I've worked on. The combustion process design was taken from the M270 base engine, the so called BlueDirect process, includes stratified low load, lambda 1 mean load and turbine temperature driven enrichment at WOT as well as ignition and injection cycling during one stroke, depended on load and engine speed. That design for the combustion process management goes quite along with the NEDC. RDE was that time no issue
We saw many irregular combustion phenomena: oil induced pre-ignition, random but heavy knock (up to 300 bar cylinder pressure) and other stuff. At that BMEP or peak cylinder level the integrity and flex of the liner and piston plays a big role. Mercedes was/is using an Aluminum-Alloy system on the block architecture as well on the liner, the latter I am not too sure, just the base block uses Alu there. If there is too much flexibility in the liner system oil issues are programmed and affects of course the combustion. We made simulations of the block structure during operation and measurements, which made clear the system, which was designed with lower cylinder pressures in mind, but still within the spec'd range, that torsional tension and bending forces de-shape some liners, especially at the corners. This lead to oil management issues, which couldn't be measured, that engine has the lowest oil consumption on the market, but if tiny oil droplets get burned, the effect can be huge, especially in a homogeneous mixture combustion regime.
Pre-ignition and many other irregular combustion phenomena are predominately happening in lower engine speed and under high load conditions. If those happen in higher engine speed region the heat management likely show issues. Because in that cases the self ignition delay is shortened by massive temperature increase, e.g. due to highly retarded WOT IGT, which can lead to glow knock or pre-ignition. In that case it is clear that is no race engine
. At the Green Hell these cars perform not bad, but the Honda Type R was with significant less power (-100 hp) 5 s faster. That speaks for it self
. If you would have seen the Honda Type R engine (K20C1) in detail, it's not the engine alone, responsible for that success
. Looks like a VW EA113 2-Liter turbo engine, which we actually use for our 1200 hp drag Audi Quattro - like a loooooooooot of work